[meteorite-list] A small Al Mahbas testimonial (& RainbowOlivine!)

From: Norman Lehrman <nlehrman_at_meteoritecentral.com>
Date: Sat Dec 18 15:09:57 2004
Message-ID: <20041218200954.29288.qmail_at_web81008.mail.yahoo.com>

Jeff,

Such a play of colors is seen in quite a number of
minerals, and is known as the "schiller effect".
Although different in technical detail, it is an
optical phenomenon very similar to the fire in
precious opal or the "labradorescence" of the feldspar
labradorite (often seen in the dark blue-gray facing
stone of bank counters, etc.) It is not related to
internal fractures, but rather to interference
patterns set up by crystal twinning, the regular
exsolution of other mineral phases, or other
systematically arrayed inclusions in the crystal
lattice.

Although not a formal term, it is quite appropriate to
call these "fire olivines" (as in "fire opal" ). I
found some beautiful fire garnets this year, the first
time I have seen this in garnets in my career---which
is why I happen to have recently reviewed "schiller".
Your specimens are the first time I've ever seen this
in olivines! Very cool.

Cheers,
Norm

--- tracy latimer <daistiho_at_hotmail.com> wrote:

> Aloha, Jeff!
> Often you will see on quartz crystals with internal
> fractures that the
> fracture has turned into a kind of prism, and light
> refracting through the
> split makes the crystal appear to have a rainbow
> along the cleavage. Maybe
> the olivine crystals that are rainbowed have the
> same thing going on. Not
> having your slice to personally look at, I can only
> speculate, though.
>
> Happy holidays!
> Tracy Latimer
>
> >
> >G'day Tracy and List,
> >
> >I certainly agree. I was lucky enough to get a nice
> piece from Mike (thanks
> >Mike) which I have put onto a page at my site. What
> is really amazing about
> >this piece is that one of the olivine crystals has
> a rainbow effect/colour.
> >Hard to describe so the pics are here:
> >
>
>http://www.meteoritesaustralia.com/features/almahbas.html
> >
> >If anyone has any opinions about how this would
> form or occur, I'd
> >certainly
> >like to hear them.
> >
> >Cheers,
> >
> >Jeff Kuyken
>
>
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Received on Sat 18 Dec 2004 03:09:54 PM PST